Generally, in a wireless communication system, in particular, in a multi-cell environment in which all cells use the same frequency band, terminals present on the boundary of each cell have a considerably limited system capacity near the cell boundary due to a large number of interference signals from neighboring cells. The reason for the phenomenon whereby performance on the cell boundary is greatly deteriorated in this way is that a Signal-to-Interference-Noise power Ratio (SINR) decreases due to interference between neighboring cells.
In order to solve this problem, research into methods of minimizing the influence of interference signals between neighboring cells has been widely carried out.
In particular, a conventional Minimum Mean Square Error (MMSE) technique is known as a considerably efficient method of mitigating neighboring cell interference signals. However, when such an MMSE technique is applied to a terminal having N receiving antennas, only N−1 interference events can be suppressed. Thus, such a technique is disadvantageous in that it is considerably inefficient in an environment in which a number of neighboring cell interference events equal to or greater than the number of receiving antennas are present.
Meanwhile, a conventional Maximum Likelihood (ML) technique can guarantee optimal reception performance regardless of the number of interference events unlike the MMSE technique, but is disadvantageous in that reception complexity greatly increases according to the number of neighboring cell interference events.
Due to interference between neighboring cells, a terminal located near the boundary of a cell may not receive data, or may have very low spectral efficiency because of its high Packet Error Rate (PER) even if it receives data. In particular, when a user located near the cell boundary is provided with a real-time traffic service that requires a Constant Bit Rate (CBR) and Quality of Service (QoS) related to time delay, high channel coding rate, a low modulation method, and a frequent retransmission rate are required so as to satisfy QoS, thus deteriorating the performance of the entire system.
Accordingly, since services satisfying various types of QoS cannot be supported without increasing the spectral efficiency of users on a cell boundary, an increase in the spectral efficiency of terminals near the cell boundary is essential to the improvement of the performance of the entire system.